Skip to content

Instantly share code, notes, and snippets.

What would you like to do?
Fix errors thrown by singleton during multiprocessing in python with environment variables
import time
from joblib import Parallel, delayed
import os
class OnlyOne:
"""Singleton Class, inspired by
Modified to work with parallel processes using environment
variables to store state across processes.
class __OnlyOne:
def __init__(self, arg):
if arg is None:
raise ValueError("Pretend empty instantiation breaks code")
self.val = arg
def __str__(self):
return repr(self) + self.val
instance = None
def __init__(self, arg=None):
if not self.instance:
if arg is None:
# look up val from env var
arg = os.getenv('SINGLETON_VAL')
# set env var so all workers use the same val
os.environ['SINGLETON_VAL'] = arg
self.instance = self.__OnlyOne(arg)
self.instance.val = arg
def __getattr__(self, name):
return getattr(self.instance, name)
def worker(num):
"""Single worker function to run in parallel.
Assume that this function has to do an empty
instantiation of the singleton.
one = OnlyOne()
one.val += num
return one.val
# Instantiate singleton
one = OnlyOne(0)
# Run in parallel worry-free
res = Parallel(n_jobs=-1, verbose=10)(
delayed(worker)(i) for i in range(10)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment